Oil-impregnated armature



1.. P. KONGSTED 1,950,986

OIL IMPREGNATED ARMATURE March 13, 1934.

Filed June 3, 1953 I INVENTOR. [yd/17 /C? KOflqs/ad QM/Z ,QJA/

ATTORNEY.

Patented Mar. 13, 1934 UNITED STATES PATENT OFFICE OIL-IMPREGNATED ARMATURE Ludvig P. Kongsted, Springfield, Mass, assignor to United American Bosch Corporation, Springfield, Mass, a corporation of New York Application June 3, 1933, Serial No. 674,192

3 Claims.

This invention relates to improvements in armatures; and especially armatures bearing windings in which currents of high tension are produced.

} 5 An object of the invention is to provide an armature which is adapted for use in a high tension magneto for ignition apparatus and which is so constructed that the insulation on the armature can be safeguarded against impairment under heavy electrical stresses; with the result that the life of the armature is prolonged and its serviceability greatly increased.

Armatures of this type generally carry a low tension or primary winding and a high tension or secondary winding. Owing to th fact that small air spaces exist between the turns of the armature coils, corona is likely to take place,

with the formation of ionized ozone and nitrous oxide. The nitrous oxide and ozone will unite with any moisture present to create an acid which is injurious both to the insulation and to the copper conductors. From such a cause considerable damage often ensues and sooner or later the rewinding of the armature is necessary.

The phenomenon known as corona can only occur in air and is the actual breaking down of the dielectric strength of the air between high voltage conductors of different potentials as well as between the high voltage conductors and grounded metal parts. I have found that corona can be entirely prevented by filling all of the minute air spaces and pockets in the armature by some suitable substance, such as oil, Vaseline or the like compound which will form a protective film over all of the various insulating materials that are employed in the making of the armature;

thus preserving such materials against oxidation and acidification.

The nature of the invention is fully set forth in the following description, but I, of course, may

make any changes which do not depart from the principle thereof.

On the drawing:

The single figure shows a schematic diagram of .an armature which is impregnated according to this invention.

On said drawing the numeral 1 indicates the core of a shuttle wound armature to be rotatably mounted in operative relation with the poles of a magneto adapted to supply current for the ignition of explosive mixtures in internal combustion engines. The upper half of this armature is shown in section and the lower half in elevation. The core 1 has polepieces at each end; these polepieces being curved on their outer faces and having the form of cylindrical segments; giving the armature its well-known H shape. The outside insulation is indicated at 3 and the windings at 4 and 5.

The winding i is a low tension or primary coil consisting of a suitable number of turns of heavy wire and constitutes the low tension coil of the armature. The high tension or secondary winding 5 consists of many turns of fine wire. The separate turns and layers of the primary 4 may be electrically insulated from one another and i so may the separate turns and layers of the secondary 5 in any suitable way; as by coating them with enamel or covering them with some other material. On the drawing this condition is suificiently indicated by the illustration of the separate turns of the windings l and 5 out of actual contact with one another. Between the winding 4 and the winding 5 and between the individual layers of wire in each winding suitable insulation 6 is interposed, and the outside covering 3 may consist of a number of insulating layers shown at 7. Between the ends of the coils 4 and 5 and the polar projections 2 on the armature are insulating layers 8.

As stated above, I impregnate this armature with an insulating or mineral lubricating oil so as to fill all air pockets and spaces between the insulation and the conductors and thus prevent corona action. The oil is soft and lubricating in eiiect and does not give rise to any danger of Humming up the bearings if some of it is thrown out as the armature is rotated at high speed in the housing of the magneto. The film of oil which forms all through the insulation and conductors acts as a protective film and even should a slight amount of acid be generated it will not harm the conductors and the insulation.

To accomplish the impregnation the armature is placed in a basket and immersed in the insulatin oil after the armature itself has been completely wound and insulated with the usual dry varnished paper and silk insulation and then preheated to a temperature of about 210 degrees Fahrenheit for approximately four hours. The oil bath is kept in a vacuum and after the arinature been preheated it is immersed in the oil bath. and kept there for about two hours under vacuum with the oil at about to degrees Fahrenheit. Air is then admitted and the coil removed and drained in an oven at about 180 degrees Fahrenheit for not less than eight hours and then slowly cooled off.

This process impregnates the windings and insulation throughout so that a film of oil forms 2. An armature carrying a low tension winding and a high tension winding thereon in combination with insulation for said windings, said windings and said insulation being impregnated with lubricating oil.

3. An armature carrying a low tension winding and a high tension winding thereon in combination with insulation for said windings, said windings and said insulation being impregnated with petroleum jelly.

LUDVIG P. KONGSTED. 

